Both purely hand-operated spray guns and spray guns that can be operated by means of automatic means and/or robots are known. By means of spray guns, for example vehicles of any type, ships, aircraft, rooms and furniture can be painted. For filler paints, topcoat paints, solid-color paints, basecoat paints and clear lacquers in the auto repair sector, diverse spray gun models are available for selection; the guns can generally be used both for solvent-containing paints and also for water-based paints. The application of multiple paint layers is usual. The paints can consist of one component (single-component paints) or of multiple components (multi-component paints, reaction lacquers).
Spray guns also have an area of use in distributing adhesives on surfaces of any type which are to be joined to each other. In professional painting, spray guns can be used to apply spray fillers. In road construction, spray guns are used to apply marking lines or the like. Even in the foodstuffs sector they are used, for example, in the decoration of cakes or tarts. In addition, it is known to coat textiles (e.g. coated garments) and leather (e.g. auto seats and shoes) by means of spray guns.
Accordingly, the liquid coating material can have a higher or lower viscosity.
The material supply device can have different material containers, depending on the customer requirements and/or depending on the nature of the liquid material. The material feed to the spray gun can be carried out without pressure or else with pressure, depending on the system.
In many spray guns, the material containers in the basic configuration have the shape of a cylinder or a cone and, because of this configuration, are therefore in general and also at this point designated as “cups”. The following types of cup are known:
I. Flow Cups:
Here, the force of gravity and the natural flowing power of liquid material are used. Therefore, in the working position, the cup is located above the spray gun. The material flows out of an outlet out of the cup, wherein the outlet is provided either in the cup base or, in so-called “upside-down” spray gun cups, in the cup cover, into the spray gun from above and, after that, along or within a color needle as far as a nozzle. Following the exit from the nozzle, it is distributed on the surface to be coated. In the case of a compressed air operated spray gun, the material to be sprayed is entrained by the air flowing past the nozzle of the spray gun. Such flow cups are used comprehensively in the motor vehicle repair trade, in joinery workshops, furniture work stops and other handcraft and industrial operations.
Both flow cups made of metals (e.g. from aluminum) or else plastics are known and as usual. Plastic cups are frequently preferred since, as a rule, they have a lower weight than metal cups.
II. Pressure Cups:
Here, the flow cup located on the spray gun is additionally pressurized. The material is therefore, so to speak, forced to flow towards the nozzle. Such pressure cups are generally used when a highly viscous or relatively highly viscous liquid is to be sprayed and the quantity of liquid to be sprayed is less than about 1 liter.
III. Suction Cups:
Here, the cup is arranged underneath the gun. A riser tube (suction tube) extends through the cup. The air flowing past along the tube draws the material, so to speak, into the spray gun as a result of the so-called Venturi effect.
IV. Pressure Vessel:
In the case of high quantities of liquid to be sprayed, pressure vessels having a volume of about 2-5 liters are frequently used but vessels of about 50-100 liters and even larger vessels can also be obtained. The material is generally supplied directly to the spray gun through a delivery hose.
V. Spraying Methods without Cup or Vessel Fixed to the Spray Gun:
So-called “airless spray guns” manage entirely without a cup. Here, by means of a pump that is operated electrically, pneumatically or by means of an internal combustion engine, the liquid material to be sprayed from a separate vessel or other container is pressurized via a hose, tube or funnel by a diaphragm or a piston. In this way, a defined quantity can thus generally be led through a high-pressure hose as far as the nozzle of the spray gun. However, air-assisted airless spray guns are also known. Here, the material to be sprayed in the nozzle area is additionally pressurized with at least one compressed air stream. Furthermore, there are also so-called “cartridge guns”. These guns also manage entirely without a cup; by using these, for example, material-filled film bags which are used in the actual gun can be pressed out. As a rule, in such guns, a hand lever is provided in the rear area, with which a rod can be forced against a movable base of the cartridge from behind. Following actuation of the hand lever, the base moves into the interior of the cartridge and presses the material located in the cartridge forward out of a nozzle. The rod can be prevented from slipping back by means of a retaining clip or the like.
In cartridge guns, there are pure handheld pressure guns and also those with compressed air operation. In the latter guns, the material is arranged in a pipe. In one embodiment, the compressed air can act directly on the cartridge base from behind. In another embodiment, provision is made for compressed air to press on the cartridge base indirectly via a telescopic piston or a pressure rod with pressure plate or the like.
In addition, in cartridge guns and spray guns in general, an electric accumulator can be provided. Particularly high pressures can be produced thereby.
Spray gun cups that can be arranged above the spray gun, in which a compressed air connection is provided in the cover, are known from practice. A compressed air hose can be connected to this connection. As a result, the liquid located in the interior of the spray gun cup, can be pressurized, so that it can be led through the spray gun to the spray nozzle more quickly than with the aid of the force of gravity on its own.
Such spray gun cups are very well suited for the material supply to the spray gun with highly viscous or relatively highly viscous liquids. During handling, however, the compressed air hose, which extends laterally at a distance along the spray gun cup, sometimes interferes. In order at every time to ensure flawless function and safety of the pressure cup, safety valves, pressure setting valves, nonreturn valves or other material back-flow preventers must additionally be provided on these cups. The additional components require additional mounting steps and/or working steps by the user. The additional components make the material container more expensive and also increase its weight.